1. Field of the Invention
This invention relates to biodegradable non-ionic surfactants.
2. Description of the Prior Art
A wide variety of non-ionic surface-active agents are known in the art. Because of their non-ionic nature, these surface-active agents are usually stable in acid, basic and neutral media. Recently, biodegradable polyoxyalkylene copolymer surfactants have been disclosed in U.S. Pat. Nos. 3,931,337 and 4,189,609. These are prepared from individual blocks of polymers and copolymers of alkylene oxides by reaction with formaldehyde or a dialkyl carbonate. The surfactant molecules fragment into individual polyoxyalkylene glycols under the influence of biologic agents or by hydrolysis or when exposed to slightly acidic or basic conditions. Surface-active acetals and formals are disclosed in U.S. Pat. No. 2,905,719. These are ethylene oxide derivatives coupled to the residue of an alkyl alcohol having 8 to 18 carbon atoms utilizing formaldehyde or acetaldehyde. Acid-sensitive non-ionic surface-active compositions are thereby produced which are stable in basic or neutral media. Surface-activity is lost upon treating these non-ionic acetals with an acid.
In U.S. Pat. No. 2,796,401, complex formal lubricating compositions are disclosed which are the reaction product of monohydric aliphatic or aromatic alcohol, or a glycol with formaldehyde as a coupling agent. The product is made in two stages in which, in the first stage, the hemiformal of the alcohol is made by heating equal moles of the alcohol and formaldehyde. Subsequently, in the second stage, the desired molar proportion of glycol and formaldehyde is added to the hemiformal and reacted to make the desired product.
In U.S. Pat. No. 2,786,081, acetal condensation products are disclosed which are the reaction products of diethylene glycol and formaldehyde. These are useful as plasticizers for polymers including film-forming materials.